In some cases, a camera device used in a monitoring system may fail to capture a video-image due to changes in the photographing environment such as a camera failure or a lighting failure, camera tampering such as blocking or covering the lens of a camera, or the like.
Conventionally, the camera device may automatically detect some failures, but cannot automatically detect all abnormalities in image data. As an example, in a case where a dark image is outputted from the camera device, it is difficult to distinguish whether a camera failure occurs or an image of a dark object is captured. Meanwhile, if there is an observer, the observer can comprehensively determine the presence or absence of abnormalities while estimating the cause of the abnormality by empirically understanding the photographing environment.
In the related art, there is disclosed a solid-state pick-up device which is capable of detecting a failure, such as a case where no signal for the failure is outputted from an image sensor, even under the dark environment (see, e.g., Patent Document 1 or 2).
Patent Document 1: Japanese Patent Application Publication No. 2009-118427
Patent Document 2: Japanese Patent Application Publication No. 2006-033385
In a large-scale monitoring system, it is difficult for the observer to visually and immediately detect video-image abnormalities of all camera devices. Further, visual observation of the observer is not suitable practically for a small-scale monitoring system which is required to save manpower. In the case of a surveillance system for an unmanned store, a recorded video-image may be checked by the observer only when an incident has occurred without usually monitoring the store. In this case, video-image abnormalities may not be detected until the recorded video-image is visually checked at the time of the occurrence of the incident, which is problematic.
However, a damage of the camera device or the like needs to be detected more reliably and more rapidly, as a potential threat to be monitored, by using other camera devices.
In view of the above, the present invention aims to automatically detect an abnormality of image data caused by a failure of a camera device or the like by using a low-load video signal processing.